Electric-arc lamp.



No. 762,116. I PATENTED JUNE 7, 1904.

4 M. H. BAKER & S. P. WILBUR.

ELECTRIC ARC LAMP.

APPLICATION nun no. 8. 1902. no MODEL. 2 sums-sum 1.

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. PATENTED JUNE 7, 1904. M. H. BAKER & S. P. WILBUR.

ELECTRIC ARC LAMP. APPLICATION rnnn DBO. s. 902.

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PATENT OFFICE.

MALCOLM H. BAKER, OF NEWV YORK, N. Y., AND SAMUEL P. WILBUR, OF

WILKINSBURG, PENNSYLVANIA, ASSIGNORS TO WVESTINGHOUSE ELEC- TRIO &MANUFACTURING COMPANY, A

VANIA.

CORPORATION OF PENNSYL- ELECTRlC-ARC LAMP.

SPECIFICATION forming part of Letters Patent No. 762,116, dated June 7,1904.

App ication filed December 8, 1902. Serial No. 134,416. (No model.)

To all whom it may concern.-

Be it known that we, MALCOLM H. BAKER, a resident of New York, in thecounty and State of New York, and SAMUEL P. WILBUR, a resi- V 5 dent ofWVilkinsburg, in the county of Allegheny and State of Pennsylvania,citizens of the United States, have invented certain new and usefulImprovements in Electric Arc Lamps, of which the following is aspecification.

The object of the present invention is to provide an arc-lamp whichwhile employing electrodes consisting of a mixture of metallic salts andcarbon shall maintain an are free I 5 from all flickering andunsteadiness.

A further object is to so difluse and soften the light from the are asto render the lamp particularly adaptable for inside and store lightingand also for the examination of 001 ors and similar work.

A further object is to provide for an even and shadowless illuminationbeneath the lamp.

A further object is to provide means for governing the distribution ofthe light, so

that it may be diffused over a large area beneath the lamp orconcentrated within a comparatively small radius.

A further object is to increase the trim life of the lamp to one hundredhours.

pact lamp adaptable for use under low ceilings.

It is now well understood in the artthat the addition of certainmetallic salts to the car- 3 5 bon electrodes of an arc-lamp produces anare or vapor bridge of greatly-increased luminosity, and, further, thatthe addition of the said salts produces a greater amount of impuritiesof combustion, so that the said are is difficult to inclose, owing tothe deposit of these impurities upon the surface of the inclosing bulb.Ithas been customary in lamps employing such electrodes to point both ofthe said electrodes down and establish the are across the lower ends;also, to hold the arc in A further object is to provide a short com-'position and to fan or spread it out by means of a governing magneticfield. When burning in this manner, it is evident that the heat of thearc creates an updraft and that this draft acting against the downwardpull of the magnetic field tends to throw the arc out of a verticalpositionthat is, tends to bend the arc to one side and to force ittoward the sides of the electrodes. This dif'ficulty is largely overcomeby surrounding the arc with a small chamber; but where large electrodes.of the plate form are used the size of this chamber becomes too great toallow of its properly confining the heated air.

The varying position of the are above described is slight and in no waynoticeable in street or similar lighting; but for inside or storelighting and for the close examination of colors or goods means must beprovided for producing an arc of the same uniformity and steadiness asthe inclosed arc. We accomplish this in the following manner, referencebeing had to the annexed drawings: Two electrodes in'the form of thinbroad plates are mounted vertically and parallel in two suitable holdersand the arc established across the upper ends. This are assumes andmaintains a vertical upward-pointing position under the combinedinfluence of its own local-current field and the up air-draft created.If allowed to burn in this position, it rapidly increases in length,becomes wavering and unstable, and usually ruptures. In order torestrain this action, I locate a magnetic field below the arc andenergize this field by a winding-in shunt to the arc of such directionthat the said magnetic field attracts the are down, shortening it andlowering the voltage. The operation is now as follows: The local fieldof the arc and the air-draft, both now acting in the same upwarddirection, are constant forces, it being assumed that the current in thecircuit is approximately constant. The only Variable, therefore, is theattractive action of the shunt magnetic field, which varies with thevoltage of the are. Should the are tend to flame and increase involtage, a proportional increase takes place in the magnetic field andthe arc is restored to the normal condition. Similarly, should thevoltage drop a decrease in the field strength takes place, againrestoring normal conditions. By these means-----that is, by -causing thelocal field of the arc and the air-draft to act constantly and in unisonand by governing the are by a strong shunt-fielda light of greatsteadiness and uniformity is produced and all flicker or waveringeliminated. In order to suitably diffuse the light and direct it beneaththe lamp, we provide a large reflector above the arc and by varying theshape of the said reflector are enabled to change the area illuminatedas desired. By

the use of electrodes in the form of plates we attain alarge increase incubical contents, and thereby an increase in life.

Our invention is illustrated in the accompanying drawings, in whichFigure 1 is a vertical section through one of our lamps. Fig. 2 is adiagram of the lampcircuit under one arrangement, and Figs. 3 and 4 aregraphic illustrations of the action of the various governing forces uponthe are.

Referring to the drawings, 1 and 2 are the electrodes, the same beingclamped in suitable holders, one of which is shown at 4 in Fig. 1. Theholder of the electrode 1 is fixed,while the holder 4 of the electrode 2is movable on pivots 5 and 6, set in supports 7 and 8 in such a mannerthat the holder 4 and the carbon 2 may be swung so as to bring the upperedge of the electrode 2 into contact with the corresponding edge of theelectrode 1. A rod 9, fixed to the holder 4, passes up through thebed-plate 15 of the lamp and is attached to a flat spring 10. Thisspring carries the core 11 of a series starting-magnet 12.

In order to govern and regulate the are, a core 13 is mounted by meansof arms 14 14 and angle-pieces 4O 40 upon the bed-plate 15. This core 13carries a winding 50 in shunt to the arc. The arms 14 14 extend throughthe bed-plate, and to their upper ends are secured pole-pieces 16 16,thus forming the desired governing magnetic field.

In order to suitably diffuse the light, we place a reflector 17, ofmetal, above the globe of the lamp, the globe appearing at 18. For theconvenient suspensionof the lamp we support the reflector 17 by means ofside rods 19, secured on the bed-plate 15, and we support upon thereflector a suitable hanger 21, carrying an insulator 20, by means ofwhich the lamp can be suspended from a suitable support. The means ofattachment as between the reflector l7 and the side rods 19 19 arehollow nuts 50 50 and ja1n-nuts-51 51, the latter being adapted to litthe screw-threaded upper ends of the side rods 19 19.

Figs. 3 and 4 represent graphically the action of the various governingforces upon the are. In Fig. 3 we have an illustration of the forceswhen both a series and a shunt magnetic governing field are employed, asmay sometimes be the case. Fig. 4 shows the con ditions when the seriesfield is dispensed with. In these figures, a represents the local fieldof the are, 6 the force exerted by the upward air-draft, and c the forceexerted by the series magnetic field. These three forces all combine tothrow the arc upward and spread it out, thus increasing the voltage. Inorder to restrain the are within the normal voltage limits, these forcesare opposed by the downward pull of the shunt magnetic field, thisdownward pull being represented by d. It is evident that stability ofoperation at the normal voltage is obtained by so adjusting the strengthof d at the said normal voltage as to hold the forces a, Z), 0, and d inequilibrium at the same voltage. In order to understand the means bywhich this arrangement produces increased steadiness of operation, it isto be noted that the force 6 (the air-draft) here acts constantly andwithout deviation in direction in distinction from the ordinary lamp,wherein, as explained, this force acts variably, and thus throws the areout of line. In Fig. 4 the series field is omitted; otherwise the sameconditions prevail. The question of the omission of the said seriesfield or the use of such a field depends upon whether alternatingcurrent or direct current is employed. In direct-current service theforce of the local field is greater than with alternating current, andtherefore the series field is not so important.

The electrical connections of the lamp are shown in Fig. 2, whichexplains itself.

In place of the flat-plate electrodes shown other forms of electrodesmight be employed such as pencil electrodes, corrugated electrodes, orany preferred form.

An additional point of advantage possessed by this lamp is that theair-draft tends to carry the impurities of combustion upward, and theyare either deposited upon the upper surface of the globe 18 or upon thereflector 17 in case an opening, such as is indicated at 52 in Fig. 1,is made in the globe.

The form which the lamp naturally assumes adapts it for being placedupon the tops of trolley-poles or other poles whereby it is madeconvenient for street service.

We claim as our invention- 1. In an electric-arc lamp, a pair ofupwardly-directed electrodes so disposed that the are is spread by thenatural air-draft and by the local field of the arc, and means forcontrolling the are, consisting of a shunt-field acting in opposition tothe local field and the airdraft.

2. In an electric-arc lamp, a pair of upwardly-directed electrodes, sodisposed that the arc is spread by the natural air-draft and by its oWnlocal field, in combination With a series field adapted to assist thespreading of the arc, and a shunt-field acting in opposition to theseries field, the local arc-field and the air-draft.

3. In an electric-arc lamp, a pair of upwardly-directed electrodes,andmeans for governing the are between them and causing it to burn steadilyat a predetermined voltage, such means consisting of two or moreconstant forces acting to spread the arc in an upward direction, and anopposing force consisting of a shunt magnetic field adapted to respondto variations of voltage at the are.

Signed at New York, in the county and State I 5 of New York, this 26thday of November, 1902.

MALCOLM HQ BAKER. Witnesses:

WM. H. CAPEL, GEORGE H. STooKBRIDeE.

